High-voltage transformers are typically used to supply an X-ray tube with high voltage. On a cathode side, the high-voltage transformer supplies, for example, a negative high voltage, relative to a ground potential, and on an anode side, a positive high voltage, relative to the ground potential. In particular, a high voltage resulting therefrom between an anode of the X-ray tube and a cathode of the X-ray tube accelerates electrons emitted from the cathode, which conventionally strike the anode and are decelerated in the process, whereby, in particular, X-ray radiation is produced for imaging. However, a certain proportion of the emitted electrons is typically scattered back at the anode.
The back-scattered electrons are captured for example by a grounded metal central part of the X-ray tube, so that, in particular, a differential current is adjusted in the X-ray tube. Therefore the X-ray tube acts in particular as an asymmetric load. Due to the differential current of the X-ray tube, the high-voltage transformer is typically asymmetrically loaded on the anode side and on the cathode side in relation to a respective load current. In other words, a differential current of the high-voltage transformer is adjusted between the anode side and the cathode side, and this is proportional to the differential current of the X-ray tube.
Typically, the differential current of the X-ray tube therefore correlates with the differential current of the high-voltage transformer. The differential current of the high-voltage transformer is produced in particular in that the load current on the anode side and the load current on the cathode side differ, in particular are asymmetric. In this case a voltage asymmetry typically follows at the high-voltage transformer. However, a conventional high-voltage transformer is conventionally symmetrical in design, for which reason the voltage asymmetry can be adjusted at the conventional high-voltage transformer due to the differential current of the X-ray tube. The voltage asymmetry follows in particular from the fact that in particular different high voltages are adjusted at the anode side and the cathode side. Due to the voltage asymmetry the high-voltage transformer and/or the X-ray tube can incur damage. Furthermore, the quality of imaging can be reduced if the high-voltage transformer for the X-ray tube is used during imaging.
Two high-voltage transformers that are independent of each other are therefore conventionally used, it being possible to prevent the voltage asymmetry by way of independent control of the cathode-side and anode-side high voltages. Production and maintenance costs increase considerably as a result because, typically, even further multiple units, in particular high-voltage inverters and/or associated oscillating circuit throttles, also have to be installed due to the two high-voltage transformers.
An alternative possibility is use of a medium-voltage transformer with high-voltage cascade connected downstream, so that a complexity of a circuit arrangement having the medium-voltage transformer, the high-voltage cascade and the X-ray tube, and therewith likewise the costs, increase.
U.S. Pat. No. 4,481,654 A discloses a high-voltage transformer comprising two transformers having matching resonance frequency.